1. Field of the Invention
The present invention relates to a wheel, more particularly one, which is used with a rack, and made in such manner as to be securely and steadily joinable to a vertical tube of the rack, and of which service life is relatively long.
2. Brief Description of the Prior Art
Conventional wheels of racks can be general grouped into ones usable with racks for supporting heavy objects, and ones usable with racks for relatively light objects. Referring to FIGS. 5, and 6, a wheel 10 suitable for use with racks for heavy objects includes a wheel part, a connecting sleeve 130, and a connecting part consisting of a round platform 110 and a screw 120; the connecting sleeve 130 has a screw hole, and is screwed to the screw 120, and closely inserted into a lower end of a vertical support tube 140 of a rack for connecting the wheel 10 to the rack. Wheels suitable for use with racks for light objects are usually formed with, like wheels of office chairs, an up-projecting connecting post for insertion into a lower end of a vertical tube of a rack.
The first kind of wheels are found to have a disadvantage that the connecting sleeve 130 is prone to separate from the tube 140 and the screw 120 when the rack is being moved around, especially when the rack is loaded with heavy objects, because the sleeve 130 is merely inserted into the tube 140 without any securing means provided on the joint between both, and because the sleeve 130 is merely connected to the screw 120 by means of screw threads, and is merely supported on the round platform 110 without any securing means provided on the joint between both. Furthermore, the screw 120 can be bent and damaged due to the heavy load if the sleeve 130 becomes loose on the screw 120.
It is a main object of the present invention to provide a wheel, which can be securely and steadily joined to a vertical tube of a rack; thus, the wheel can""t become loose or separate from the rack even if the rack is being moved around with heavy load.
The wheel of this invention consists of a wheel support for holding a wheel part in position, a sleeve inserted into a lower end of one vertical tube of a rack, a supporting member joined to both the sleeve and a top of the wheel support, a screw projecting upwards from the polygonal portion and screwed into a screw hole of the sleeve, a round step-shaped portion formed on top of the supporting member to fit with a cavity on a lower end of the sleeve, a corrugated surface formed on an annular portion of the sleeve for increasing friction, and a resilient C-shaped ring fitted around an annular groove of the sleeve; the ring contacts an inner side of the tube to prevent the sleeve from separating from the tube; the annular groove is shaped so that a sideways facing annular portion thereof tapers off towards a lower end, i.e. similar to an middle section of an outer side of an inverted cone.